[X86] Add vector support to targetShrinkDemandedConstant for OR/XOR opcodes

[RKSimon]

Summary

If we only demand the lsb of a constant build vector used in a OR/XOR op then sign extend it to an allsignbits bool pattern.

This also requires SimplifyDemandedBits XOR handling to be modified to call ShrinkDemandedConstant on any (non-NOT) XOR pattern to account for non-splat cases.

Next step towards fixing PR45808 - with this patch we now get a <-1,-1,0,0> v4i64 constant instead of <1,1,0,0>.

[RKSimon]

Looking at ways to remove some of the poor codegen that still remains

[RKSimon]

Add DemandedElts support to ShrinkDemandedConstant/targetShrinkDemandedConstant which fixes the poor vector codegen

[RKSimon]

ping?

[craig.topper]

LGTM

llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp

if (ShrinkDemandedOp(Op, BitWidth, DemandedBits, TLO))
       return true;
 
     // If all of the unknown bits are known to be zero on one side or the other
     // (but not both) turn this into an *inclusive* or.
     //    e.g. (A & C1)^(B & C2) -> (A & C1)|(B & C2) iff C1&C2 == 0
     if (DemandedBits.isSubsetOf(Known.Zero | Known2.Zero))
       return TLO.CombineTo(Op, TLO.DAG.getNode(ISD::OR, dl, VT, Op0, Op1));
 
-    if (ConstantSDNode *C = isConstOrConstSplat(Op1)) {
+    ConstantSDNode* C = isConstOrConstSplat(Op1, DemandedElts);
+    if (C) {
       // If one side is a constant, and all of the known set bits on the other
       // side are also set in the constant, turn this into an AND, as we know
       // the bits will be cleared.
       //    e.g. (X | C1) ^ C2 --> (X | C1) & ~C2 iff (C1&C2) == C2
       // NB: it is okay if more bits are known than are requested
       if (C->getAPIntValue() == Known2.One) {
         SDValue ANDC =
             TLO.DAG.getConstant(~C->getAPIntValue() & DemandedBits, dl, VT);
         return TLO.CombineTo(Op, TLO.DAG.getNode(ISD::AND, dl, VT, Op0, ANDC));
       }
 
       // If the RHS is a constant, see if we can change it. Don't alter a -1
       // constant because that's a 'not' op, and that is better for combining
       // and codegen.
-      if (!C->isAllOnesValue()) {
-        if (DemandedBits.isSubsetOf(C->getAPIntValue())) {
-          // We're flipping all demanded bits. Flip the undemanded bits too.
-          SDValue New = TLO.DAG.getNOT(dl, Op0, VT);
-          return TLO.CombineTo(Op, New);
-        }
-        // If we can't turn this into a 'not', try to shrink the constant.
-        if (ShrinkDemandedConstant(Op, DemandedBits, DemandedElts, TLO))
-          return true;
-      }
-    }
+      if (!C->isAllOnesValue() &&
+          DemandedBits.isSubsetOf(C->getAPIntValue())) {
+    }
+
+    if (!C || !C->isAllOnesValue())
 
     Known ^= Known2;
     break;
   }
   case ISD::SELECT:
     if (SimplifyDemandedBits(Op.getOperand(2), DemandedBits, Known, TLO,
                              Depth + 1))
       return true;

llvm/lib/Target/X86/X86ISelLowering.cpp

 //                           X86 Optimization Hooks
 //===----------------------------------------------------------------------===//
 
 bool
 X86TargetLowering::targetShrinkDemandedConstant(SDValue Op,
                                                 const APInt &DemandedBits,
                                                 const APInt &DemandedElts,
                                                 TargetLoweringOpt &TLO) const {
-  // Only optimize Ands to prevent shrinking a constant that could be
-  // matched by movzx.
-  if (Op.getOpcode() != ISD::AND)
-    return false;
-
   EVT VT = Op.getValueType();
+  unsigned Opcode = Op.getOpcode();
+  unsigned EltSize = VT.getScalarSizeInBits();
 
-  // Ignore vectors.
-  if (VT.isVector())
+  if (VT.isVector()) {
+    // If the constant is only all signbits in the active bits, then we should
+    // extend it to the entire constant to allow it act as a boolean constant
+    // vector.
+    auto NeedsSignExtension = [&](SDValue V, unsigned ActiveBits) {
+      if (!ISD::isBuildVectorOfConstantSDNodes(V.getNode()))
         return false;
+      for (unsigned i = 0, e = V.getNumOperands(); i != e; ++i) {
+        if (!DemandedElts[i] || V.getOperand(i).isUndef())
+          continue;
+        const APInt &Val = V.getConstantOperandAPInt(i);
+        if (Val.getBitWidth() > Val.getNumSignBits() &&
+            Val.trunc(ActiveBits).getNumSignBits() == ActiveBits)
+          return true;
+      }
+      return false;
+    };
+    // For vectors - if we have a constant, then try to sign extend.
+    // TODO: Handle AND/ANDN cases.
+    unsigned ActiveBits = DemandedBits.getActiveBits();
+    if (EltSize > ActiveBits && EltSize > 1 && isTypeLegal(VT) &&
+        (Opcode == ISD::OR || Opcode == ISD::XOR) &&
+        NeedsSignExtension(Op.getOperand(1), ActiveBits)) {
+      EVT BoolVT = EVT::getVectorVT(*TLO.DAG.getContext(), MVT::i1,
+                                    VT.getVectorNumElements());
+      SDValue NewC =
+          TLO.DAG.getNode(ISD::SIGN_EXTEND_INREG, SDLoc(Op), VT,
+                          Op.getOperand(1), TLO.DAG.getValueType(BoolVT));
+      SDValue NewOp =
+          TLO.DAG.getNode(Opcode, SDLoc(Op), VT, Op.getOperand(0), NewC);
+      return TLO.CombineTo(Op, NewOp);
+    }
+    return false;
+  }
 
-  unsigned Size = VT.getSizeInBits();
+  // Only optimize Ands to prevent shrinking a constant that could be
+  // matched by movzx.
+  if (Opcode != ISD::AND)
+    return false;
 
   // Make sure the RHS really is a constant.
   ConstantSDNode *C = dyn_cast<ConstantSDNode>(Op.getOperand(1));
   if (!C)
     return false;
 
   const APInt &Mask = C->getAPIntValue();
 
   // Clear all non-demanded bits initially.
   APInt ShrunkMask = Mask & DemandedBits;
 
   // Find the width of the shrunk mask.
   unsigned Width = ShrunkMask.getActiveBits();
 
   // If the mask is all 0s there's nothing to do here.
   if (Width == 0)
     return false;
 
   // Find the next power of 2 width, rounding up to a byte.
   Width = PowerOf2Ceil(std::max(Width, 8U));
   // Truncate the width to size to handle illegal types.
-  Width = std::min(Width, Size);
+  Width = std::min(Width, EltSize);
 
   // Calculate a possible zero extend mask for this constant.
-  APInt ZeroExtendMask = APInt::getLowBitsSet(Size, Width);
+  APInt ZeroExtendMask = APInt::getLowBitsSet(EltSize, Width);
 
   // If we aren't changing the mask, just return true to keep it and prevent
   // the caller from optimizing.
   if (ZeroExtendMask == Mask)
     return true;
 
   // Make sure the new mask can be represented by a combination of mask bits
   // and non-demanded bits.

llvm/test/CodeGen/X86/promote-cmp.ll

 ; SSE2-NEXT:    movdqa %xmm4, %xmm7
 ; SSE2-NEXT:    pcmpgtd %xmm5, %xmm7
 ; SSE2-NEXT:    pcmpeqd %xmm5, %xmm4
 ; SSE2-NEXT:    pshufd {{.*#+}} xmm4 = xmm4[1,1,3,3]
 ; SSE2-NEXT:    pand %xmm7, %xmm4
 ; SSE2-NEXT:    pshufd {{.*#+}} xmm5 = xmm7[1,1,3,3]
 ; SSE2-NEXT:    por %xmm4, %xmm5
 ; SSE2-NEXT:    shufps {{.*#+}} xmm5 = xmm5[0,2],xmm6[0,2]
-; SSE2-NEXT:    movaps {{.*#+}} xmm4 = <1,1,u,u>
-; SSE2-NEXT:    xorps %xmm5, %xmm4
-; SSE2-NEXT:    shufps {{.*#+}} xmm5 = xmm5[2,1,3,3]
+; SSE2-NEXT:    pcmpeqd %xmm4, %xmm4
+; SSE2-NEXT:    movaps %xmm5, %xmm6
+; SSE2-NEXT:    shufps {{.*#+}} xmm6 = xmm6[2,1],xmm5[3,3]
+; SSE2-NEXT:    psllq $63, %xmm6
+; SSE2-NEXT:    psrad $31, %xmm6
+; SSE2-NEXT:    pshufd {{.*#+}} xmm6 = xmm6[1,1,3,3]
+; SSE2-NEXT:    pand %xmm6, %xmm1
+; SSE2-NEXT:    pandn %xmm3, %xmm6
+; SSE2-NEXT:    por %xmm6, %xmm1
+; SSE2-NEXT:    shufps {{.*#+}} xmm5 = xmm5[0,1,1,3]
+; SSE2-NEXT:    xorps %xmm4, %xmm5
 ; SSE2-NEXT:    psllq $63, %xmm5
 ; SSE2-NEXT:    psrad $31, %xmm5
-; SSE2-NEXT:    pshufd {{.*#+}} xmm5 = xmm5[1,1,3,3]
-; SSE2-NEXT:    pand %xmm5, %xmm1
-; SSE2-NEXT:    pandn %xmm3, %xmm5
-; SSE2-NEXT:    por %xmm5, %xmm1
-; SSE2-NEXT:    pshufd {{.*#+}} xmm3 = xmm4[0,1,1,3]
-; SSE2-NEXT:    psllq $63, %xmm3
-; SSE2-NEXT:    psrad $31, %xmm3
-; SSE2-NEXT:    pshufd {{.*#+}} xmm3 = xmm3[1,1,3,3]
+; SSE2-NEXT:    pshufd {{.*#+}} xmm3 = xmm5[1,1,3,3]
 ; SSE2-NEXT:    pand %xmm3, %xmm0
 ; SSE2-NEXT:    pandn %xmm2, %xmm3
 ; SSE2-NEXT:    por %xmm3, %xmm0
 ; SSE2-NEXT:    retq
 ;
 ; SSE4-LABEL: PR45808:
 ; SSE4:       # %bb.0:
 ; SSE4-NEXT:    movdqa %xmm0, %xmm4
 ; SSE4-NEXT:    movdqa %xmm1, %xmm0
 ; SSE4-NEXT:    pcmpgtq %xmm3, %xmm0
 ; SSE4-NEXT:    movdqa %xmm4, %xmm5
 ; SSE4-NEXT:    pcmpgtq %xmm2, %xmm5
 ; SSE4-NEXT:    pshufd {{.*#+}} xmm5 = xmm5[0,2,2,3]
-; SSE4-NEXT:    pxor {{.*}}(%rip), %xmm5
+; SSE4-NEXT:    pcmpeqd %xmm6, %xmm6
+; SSE4-NEXT:    pxor %xmm5, %xmm6
 ; SSE4-NEXT:    psllq $63, %xmm0
 ; SSE4-NEXT:    blendvpd %xmm0, %xmm1, %xmm3
-; SSE4-NEXT:    pmovzxdq {{.*#+}} xmm0 = xmm5[0],zero,xmm5[1],zero
+; SSE4-NEXT:    pmovzxdq {{.*#+}} xmm0 = xmm6[0],zero,xmm6[1],zero
 ; SSE4-NEXT:    psllq $63, %xmm0
 ; SSE4-NEXT:    blendvpd %xmm0, %xmm4, %xmm2
 ; SSE4-NEXT:    movapd %xmm2, %xmm0
 ; SSE4-NEXT:    movapd %xmm3, %xmm1
 ; SSE4-NEXT:    retq
 ;
 ; AVX1-LABEL: PR45808:
 ; AVX1:       # %bb.0:
 ; AVX1-NEXT:    vextractf128 $1, %ymm1, %xmm2
 ; AVX1-NEXT:    vextractf128 $1, %ymm0, %xmm3
 ; AVX1-NEXT:    vpcmpgtq %xmm2, %xmm3, %xmm2
 ; AVX1-NEXT:    vpcmpgtq %xmm1, %xmm0, %xmm3
-; AVX1-NEXT:    vpcmpeqd %xmm4, %xmm4, %xmm4
-; AVX1-NEXT:    vpxor %xmm4, %xmm3, %xmm3
 ; AVX1-NEXT:    vinsertf128 $1, %xmm2, %ymm3, %ymm2
+; AVX1-NEXT:    vxorpd {{.*}}(%rip), %ymm2, %ymm2
 ; AVX1-NEXT:    vblendvpd %ymm2, %ymm0, %ymm1, %ymm0
 ; AVX1-NEXT:    retq
 ;
 ; AVX2-LABEL: PR45808:
 ; AVX2:       # %bb.0:
 ; AVX2-NEXT:    vpcmpgtq %ymm1, %ymm0, %ymm2
 ; AVX2-NEXT:    vpxor {{.*}}(%rip), %ymm2, %ymm2
-; AVX2-NEXT:    vpsllq $63, %ymm2, %ymm2
 ; AVX2-NEXT:    vblendvpd %ymm2, %ymm0, %ymm1, %ymm0
 ; AVX2-NEXT:    retq
   %3 = icmp sgt <4 x i64> %0, %1
   %4 = xor <4 x i1> %3, <i1 true, i1 true, i1 false, i1 false>
   %5 = select <4 x i1> %4, <4 x i64> %0, <4 x i64> %1
   ret <4 x i64> %5
 }

llvm/test/CodeGen/X86/setcc-lowering.ll

 ; AVX:       # %bb.0: # %entry
 ; AVX-NEXT:    vandps {{.*}}(%rip), %ymm0, %ymm0
 ; AVX-NEXT:    vextractf128 $1, %ymm0, %xmm1
 ; AVX-NEXT:    vpxor %xmm2, %xmm2, %xmm2
 ; AVX-NEXT:    vpcmpeqd %xmm2, %xmm1, %xmm1
 ; AVX-NEXT:    vpcmpeqd %xmm2, %xmm0, %xmm0
 ; AVX-NEXT:    vpackssdw %xmm1, %xmm0, %xmm0
 ; AVX-NEXT:    vpor {{.*}}(%rip), %xmm0, %xmm0
-; AVX-NEXT:    vpsllw $15, %xmm0, %xmm0
-; AVX-NEXT:    vpsraw $15, %xmm0, %xmm0
 ; AVX-NEXT:    vzeroupper
 ; AVX-NEXT:    retq
 ;
 ; KNL-32-LABEL: pr25080:
 ; KNL-32:       # %bb.0: # %entry
 ; KNL-32-NEXT:    # kill: def $ymm0 killed $ymm0 def $zmm0
 ; KNL-32-NEXT:    vptestnmd {{\.LCPI.*}}{1to16}, %zmm0, %k0
 ; KNL-32-NEXT:    movb $15, %al